Clearway, Stopway, Threshold, TORA, TODA, ASDA, LDA | Calculation of Minimum Line-Up Distance Correction

The following terms describe areas of defined dimensions under the control of the appropriate authority, declared as suitable for takeoff and landing purposes:

CLEARWAY

A clearway is the area beyond the runway, over land or water, over which an aircraft can make a portion of its initial climb to a specified height. Its width should not be less than 152 meters, centrally located about the extended centerline of the runway. The clearway is expressed as a plane extending from the end of the runway with an upslope not exceeding 1.25%, above which no object or terrain protrudes, except for threshold lights. Its length should not be more than half the runway length.

STOPWAY

Stopway is the area at the end of take-off runway no less wide than the runway and centered upon extended centerline of runway and able to support the aeroplane during an aborted take-off without causing structural damage to the aeroplane.

THRESHOLD

The threshold is the beginning of the portion of the runway that is usable for landing. The threshold must be at or beyond the point where the obstacle clearance plane intersects the runway. For this reason, the threshold may be displaced from the beginning of the runway.

TORA (Take off Run Available)

TORA (Takeoff Run Available) is the length of runway that is available and suitable for the ground run of an aeroplane during takeoff. TORA does not include the stopway or clearway. TORA is either equal to the runway length, or to equal to distance from runway entry point (intersecting taxiway) to the end of the runway.

TODA (Take off Distance Available)

TODA is the sum of length of takeoff run available and length of clearway available. In case no clearway exists, TODA is same as TORA. TODA includes ground as well as air segments.

ASDA (Accelerate-Stop Distance Available)

ASDA (Accelerate-Stop Distance Available) is defined as the length of the takeoff run available plus the length of the stopway. ASDA is an important factor in determining the V1 speed. In the event of an aborted takeoff, the aircraft can be brought to a stop either on the runway or on the stopway.

ASDA must not be used as TORA.

LDA (Landing Distance Available)

LDA is the runway length declared available and suitable for ground run of aeroplane landing.

Information on Clearway, Stopway, TORA, TODA, ASDA & LDA for different runways can be obtained from Aerodrome Information Publications, Jepessen Charts and RTOW charts.